Since the development of polymers, injection molding processes have gained widespread use due to the ease at which plastics may be melted and cooled to form a desired component. In addition, injection molding is very versatile as it may create parts ranging from only a few millimeters in size to parts that are several meters wide. Injection molding may also produce simple components to components having very intricate details.
While injection molding enjoys widespread use, there is a significant initial cost for an injection molding process due to the molds being expensive to manufacture. Consequently, injection molding is most common for components that are to be mass produced, as the cost of the injection mold may then be amortized over thousands or even hundreds of thousands of components.
Typical molds are constructed from materials, such as aluminum or hardened steel. The choice of what type of material to use in building a mold is largely a question of economics. For instance, the question of whether to build an aluminum or steel mold may depend on considerations related to economics, including the expected life-cycle of the product, the volume of products to be produced, the capital currently available, the size of the mold, the tolerances that need to be maintained, as well as other considerations. While aluminum and steel are readily available for virtually any size of mold, an aluminum mold may be produced at a relatively low cost, and may still be used to mold ten thousand or more parts. If, for example, a company expects to produce only ten thousand parts, the company may select an aluminum mold. In contrast, if a hundred thousand parts are going to be required, the same company may chose to produce the mold from a hardened steel, which exhibits an increases wear resistance relative to aluminum, even if the initial cost of the steel mold is five or more times that of the aluminum mold. Thus, despite the higher initial cost, steel molds may be more economical over the full product run due to an increased lifespan. Indeed, it is not uncommon for a single steel mold to be used to produce hundreds of thousands, or even millions of parts before it wears out.
While steel and aluminum are the most common materials used in manufacturing molds, other materials have also been used. Other materials are typically used, however, where considerations other than cost and mold lifecycle become significant. For instance, due to product details, a mold may be produced to dissipate heat more quickly than aluminum or steel. If temperatures are sufficiently large or prolonged, the injected plastic material may be damaged. Consequently, beryllium-copper alloys are sometimes used in injection molds due to their heat dissipation properties.
Despite the widespread use of steel and aluminum, and to a lesser extent beryllium-copper alloys, in injection molding processes, such materials each exhibit characteristics upon which improvements may be made.